The present disclosure relates to an image forming apparatus developing an electrostatic latent image.
An electrographic image forming apparatus, such a copying machine, a printer or a facsimile, uses processes of supplying a toner (a developer) to an electrostatic latent image formed on a surface of an image carrier, such as a photosensitive drum, developing the electrostatic latent image as a toner image and transferring and fixing the toner image to a recording medium.
In such an image forming apparatus, as the toner image is formed on the surface of the photosensitive drum, the toner is consumed. Therefore, in order to maintain a fixed quantity of toner density (a rate of the toner to a carrier) of the developer contained in a development device, the toner is supplied to the development device from a toner cartridge.
Generally, a composition of the toner in the toner cartridge is same as the toner existing in the development device in advance. Thereby, a change in hue and a change of an electric charge amount when the toner cartridge is replaced are restrained as possible.
However, the composition of the toner in the toner cartridge may be changed according to running change, compatibility or the like. Then, when the electric charge amount of the toner in the toner cartridge is different from the electric charge amount of the toner existing in the development device, it is feared that developability is varied according to a mixture quantity and an image quality of a printed matter is degraded.
To such problems, for example, a method of detecting identification information from a toner cartridge having the identification information for identify characteristics of the inner toner and controlling copying process condition on the basis of the identification information is proposed. In this method, when a replacement rate of the toner reaches fifty percent, the control of the copying process condition is started.
Moreover, in another proposed method, when another toner cartridge for another toner having different composition from a toner existing in a development device in advance is installed, a consumption of the toner is added up until the toner existing in the development device in advance is replaced to the new toner. On the basis of the addition of the toner consumption, a form factor and particle diameter of the toner and other factors, parameters in relation to a development bias are changed.
However, a mixing rate of new replenishment toner and toner existing in the development device in advance continues varying all until the toner is completely replaced. By contrast, in the above-mentioned former method, because the control of the copying process condition is started when the toner replacement rate is reached to fifty percent, the image quality of the printed matter often becomes unstable.
In addition, the mixing rate of the new replenishment toner and the toner existing in the development device in advance is varied according to temperature, humidity and toner density. By contrast, in the above-mentioned latter method, because the temperature, humidity and toner density are not taken into account, the image quality of the printed matter is not sufficiently stabilized.
Thus, in the above-mentioned methods, the image quality of the printed matter is not stabilized until the toner existing in the development device in advance is completely replaced by the new replenishment toner. Therefore, an image forming apparatus capable to early stabilize the image quality is required.